Electrolytic cell



July 18, 1950 J. c. scI-IUMACHER ELECTROLYTEC CELL 2 Sheets-Sheet l Filed OOC. 3l, 1945 INvEINToR JOSEPH C. SCHUMACHER BYWVM/Am l |l IIIIIIIIII III IIL 1 IL.. I

FI .lIIL

HUUHHU ATTORNEY July 18, 1950 J. c. scHUMAcHER 2,515,514

ELECTROLYTIC CELL Filed Oct. 51, 1945 2 Sheets-Sheet 2 @n r V/VV n/ AL b\\ l@ l A INVENTGR JOSEPH ,Q SCHUMACHER ATTORNEY Patented July 18, 1950 UNITED STATES PATENT OFFICE c ELECTROLYTIC CELL Joseph C. Schumacher, Los Angeles, Calif., as-

signor to Western Electrochemical Company, Los Angeles, Calif., a corporation of Nevada Applicatin october 31, 1945, serial N0. 625,858

(o1. 2in- 274) 3 Claims. l

This invention relates to an electrolytic cell and in particular to an apparatus for the electrochemical lconversion of aqueous sodium chloride to sodium chlorate.

One object `of the invention is to provide an electrolytic cell for a continuous electrolytic process. Another object is to provide an electrolytic cell for the economical production of sodium -chlorate by the electrolysis of aqueous sodium chloride. A further object is to provide an improved structure in electrolytic cells and in assembled graphite electrodes which facilitate removal and replacement of the electrodes. Still another object is to provide an explosion-proof electrolytic chlorate cell. Another object is to provide a twin-cell chl-crate cell structure having improved operating and structural characteristics.

These and other objects lare attained by my invention which will be understood from the following description and the accompanying drawings in which: l

Fig. l is a plan view of my electrolytic cell with parts broken away to show the interior arrangement; 'l

Fig. 2 is a side elevation of the same with parts broken Iaway to show the interiorarrangement;

Fig. 3 is an end elevational view of the cell shown in Figs. 1 and 2; p

Fig. 4 is an enlarged cross-sectional View showing the mounting of the graphite anode, taken on the line -4-4 of Fig. 2.

My electrolytic cell is particularly adapted for the electrochemical conversion of aqueous sodium chloride to sodium chlorate, and will be described in connecti-on -with that process, although its use is not :limited to this electrochemical process. I have found that this reaction may be carried out as a continuous now process, with high efliciency, minimum danger from explosions, and with certainty of control of the conditions of electrolysis within the cell for optimum production by the use of this new and improved electrolytic chlorate cell. The cell structure does not include a separating diaphragm between the anode and cathode portions and therefore may be used for other electrochemical processes in which such an arrangement is permissible and desired.

In general my chlorate cell consists of a rectangular trough-like steel tank having an electrically insulating cover through which vertically disposed graphite electrodes extend into the cavity of the tank. The cell is provided with banks of cooling tubes arranged in vertical tiers between parallel rows of anodes, these cooling tubes also serving as cathodes in the electrochemical reaction. The walls of the steel tank also serve as cathodes. The steel tank is adapted to contain the electrolyte which is circulated lengthwise through the cell, with suitable baille plates for creating turbulence and mixing in the electrolyte.

The preferred form of my electrolytic cell as shown in the drawings consist of a twin arrangement of pairs of electrodes housed in a single tank divided by a lengthwise vertical partition, since it has been found that this arrangement gives good operating conditions, saves considerable space in setting up large banks of cells, and allows economy in the use of the structural materials. Referring to the drawings, the steel tank Il is of welded steel construction and is of elongated trough-like structure to provide space for parallel rows of electrodes. For the twin cell structure, a partition member l2 dividing the cell into two elongated compartments is provided, this partition conveniently being a perforated steel plate with openings I3 in the electrolyte portion to permit the iiow of electrolyte from one half-cell to the other. A heavier structural steel member i4 having a fiat horizontal surface is welded to the top edge of the partition plate l2 to provide a iirm support surface for the cover plates for the cell. The upper edges of the cell walls are provided with outturning anges l5 which together with the top edge of the structural member I4 provide means for supporting and attaching the electrically insulating cover plate I6. The cover plate, conveniently made in sections, is bolted to the flanges l5, and the sections are provided with openings for the insertion of the graphite electrodes lli. The side walls of the steel tank ll and the partition l2 are held rigidly in position by welded cross braces il, disposed as required for structural strength throughout the length and height of the cell, and placed to avoid Contact or too close proximity to the anodes.

The cover plate i6 is conveniently made of compressed sheets of asbestos-Portland cement composition or an equivalent electrically non-conductive and corrosion-resistant material, in which slots is are provided for four rows of graphite anodes lli, two in each half-cell on both sides of the partition member l2.

The anodes are constructed of dense graphite or graphitized carbon plates mounted in a cast lead block 20 with copper dowel pins 2l for maintaining good electrical and mechanical connection between the graphite and the lead. These lead block members are conveniently made by casting the lead around the ends of the graphite plates and dowel pins, and headed stud bolts 22,

for use in making electrical connections to the bus bars, are conveniently cast at the same time into the lead block extending upwardly from its upper surface.

Banks of steel cooling water tubes are provided longitudinally between pairs of rows of graphite anodes, these tubes being supported in the perforated steel end plates .24 oi the tank l I forming one wall of the manifolds 24A at the ends of the cells, with suitable horizontal bales 25 to regulate the now of cooling water in portions of the bank of tubes, as desired, from one end to the other, to provide uniform temperature throughout the space in which the electrolysis takes place. These steel water cooling tubes 23 also serve as cathode surfaces along with the `walls and the par tition member l2 of the steel tank H. Electrical connection for the cathodes is conveniently made by an upstanding longitudinal bar 25 welded to the edge of the tank flange l along one side of f the cell, with suitably spaced connector bolts provided therein. The cooling water is introduced to the manifold at one end by the inlet pipe 2.9 and is removed through the outlet pipe 29A.

A settling space is provided below the anodes and the water cooling tubes for the accumulation of sediment, mostly derived from the disintegration of the graphite anodes, a clean-cut hole 28 being provided at the ends of the cells.

The space between the electrolyte and the cover plate IS serves for the collection of the gases which are formed during the electrochemical reactions. When the cell is used for the electrolysis oi sodium chloride to form sodium chlorate, or in similar reactions, the gases which are evolved are hydrogen, oxygen, and chlorine, and sometimes carbon dioxide. These gases accumulate in explosive proportions, and in the device of this invention are removed and rendered non-explosive by sweeping out this gas space with large quantities of air or other inert gas. An inlet pipe 3l introduced through and mounted on a specially formed section ISA of the cover plate I5 near the end of the cell serves to bring in the inert gas, and a similarly placed outlet pipe 30 at the other lend of the cell is provided for removal of the mixture of the inert gas with the gases generated in the cell.

The electrolyte is brought into the cell by means of inlet pipes 33 at one end of the cell, and overflow outlet pipes 34 at the other end of the cell are used to remove the excess electrolyte to maintain its upper level at a desired height.

In certain electrochemical reactions, it is desirable to circulate the electrolyte in and out of the cell. My cell is adapted particularly for use in a. continuous circulating process in which the electrolyte enters at one end and passes in contact with a relatively long row of electrodes where the electrochemical transformation takes place, following `which the effluent electrolyte is removed from the opposite end; outside the cell it may be chemically treated, or additions of material may be made, or portions of the formed product may be removed from the eiiiuent electrolyte, or it may be merely recirculated in and out in order to again contact the electrodes of the cell and be subjected again to electrolysis.

In the twin cell arrangement of my preferred form, as shown in the drawings, each hahc cell is provided with an inlet pipe and an outlet pipe for the electrolyte, but the partition member l2 is provided with many openings so that, in fact, the electrolyte circulates between the half cells. When a half-cell only is used, the electrolyte circulates from one end to the other, with mixing and turbulence provided by bailles and tube supports,

The advantages of my electrolytic cell structure, particularly for use in making sodium chlorate and similar reactions, will be apparent. The advantages of the continuous flow electrolytic process for making sodium chlorate using a cell of the preferred type shown here are explained in detail in my copending patent application, Serial No. 625,856, iiled October 31, 1945, now Patent Number 2,511,516. One important advantage of my cell structure for any suitable electrochemical process consists in the provision of means for getting the optimum operating eiciency, including the certainty of uniformity in the temperature throughout the electrolyte, by the use of the cooling coils placed close to the electrodes, combined with baille structure to bring about turbulence and mixing. Unusually high current densities on both the anode and the cathode may be employed because of the means provided for insuring uniformity in temperature and the avoidance of local overheating and this improves the electrochemical eiciency. The optimum values for electrode current densities and temperature for the particular electrochemical reaction may be constantly maintained because of the mixing and the continuous ow of electrolyte through the cell. In a bank of many cells, the maintenance of uniform load conditions on each cell gives a good power load factor for the plant. Another advantage of my cell structure is the provision of means to prevent explosion by sweeping out the generated explosive gases with an inert gas. The advantage of using the twin cell arrangement includes the saving in structural material and space.

While I prefer to use the twin cell arrangement as described, it will be obvious that the half cell arrangement in which the partition constitutes the side wall of the cell tank with two rows of anodes as shown for each half cell, may also be employed.

The mounting for the graphite anodes in the lead slab is a particularly advantageous arrangement. The heavy weight of the lead slab keeps the electrodes in place in the cell without other attaching means and permits easy sealing of the cover portion of the cell, a layer of plastic gasket material between the lead and the top surface of the insulating cover plate serves to removably seal the assembly to the cell cover. Another marked advantage of my anode assembly is that mounted electrode units may be quickly removed and new ones replaced in the cells without serious interruption of the electrochemical process.

I claim:

l. An electrolytic cell comprising an elongated steel tank adapted to contain an aqueous electrolyte and to serve as cathode; an electrically insulating cover attached to said tank, said cover having elongated electrode slots extending longitudinally of said cover; an anode member for said cell including unit assemblies each consisting of a weighted electrically .conductive mounting block having two spaced apart parallel graphite plates mechanically and electrically connected thereto, said plates extending into the electrolyte space in said tank through said elongated slots in said cover to form parallel rows of graphite electrodes, said block having a coinciding face in contact with said cover whereby to seal the openings in said cover for said electrodes, said assemblies being arranged in rows lengthwise of said tank; means for maintaining temperature uniformity in the electrolyte including parallel manifolded pipes for the circulation of liquid coolingl mdium, disposed between the rows of graphite electrodes; and means for controlling the circulation of the electrolyte through the cell and around the electrodes including baiiles, inlet pipes and overflow discharge openings.

2. An electrolytic cell comprising an elongated steel tank adapted to contain an aqueous electrolyte and to serve as cathode; an electrically insulating cover attached to said tank, said cover having elongated electrode slots extending longitudinally oi said cover; an anode member for said cell including unit assemblies each consisting of a lead mounting block for hol-ding two spaced apart parallel graphite plates, said graphite plates being mechanically and electrically connected to said mounting blocks, said plates extending into the electrolyte space inr said tank through the slots in said cover to form parallel rows of graphite anodes, said block having a coinciding face in contact with said cover whereby to seal the openings in said cover for said electrodes, said assemblies being arranged in rows lengthwise of said tank; means for maintaining temperature uniformity in the electrolyte including parallel manifolded pipes for the circulation of cooling medium disposed between said rows of graphite anodes; means for controlling the circulation of the electrolyte around the electrodes and from ne end of the cell to the other including baffles, inlet pipes, and overflow discharge openings; and conduit means for introducing gas to and withdrawing gas from the space between the cell cover and the upper level of the electrolyte.

3. An electrolytic cell having a steel tank 35 adapted to contain an aqueous electrolyte and to serve as the cathode, an electrically insulating cover attached to said tank, said cover having elongated electrode slots; an anode member consisting of a plurality of anode assemblies, each assembly consisting of a lead block cast around the ends o f two graphite plates disposed apart in parallel arrangement, said block having a coinciding face for contact with said cover whereby to seal the openings in said cover for said electrodes, said graphite plates being mechanically supported by and electrically connected with said lead mounting blocks, the free ends of said graphite plates extending through said slots in said cover; the weight of said block being suliicient to hold'said electrodes in place in said cell and to seal the openings in said cover.

JOSEPH C. SCHUMACHER.

REFERENCES CITED The following references are of record in the ille of this patent:

UNITED STATES PATENTS 

1. AN ELECTROLYTIC CELL COMPRISING AN ELONGATED STEEL TANK ADAPTED TO CONTAIN AN AQUEOUS ELECTROLYTE AND TO SERVE AS CATHODE; AN ELECTRICALLY INSULATING COVER ATTACHED TO SAID TANK, SAID COVER HAVING ELONGATED ELECTRODE SLOTS EXTENDING LONGITUDINALLY OF SAID COVER; AN ANODE MEMBER FOR SAID CELL INCLUDING UNIT ASSEMBLIES EACH CONSISTING OF A WEIGHTED ELECTRICALLY CONDUCTIVE MOUNTING BLOCK HAVING TWO SPACED APART PARALLEL GRAPHITE PLATES MECHANICALLY AND ELECTRICALLY CONNECTED THERETO, SAID PLATES EXTENDING INTO THE ELECTROLYTE SPACE IN SAID TANK THROUGH SAID ELONGATED SLOTS IN SAID COVER TO FORM PARALLEL ROWS OF GRAPHITE ELECTRODES, SAID BLOCK HAVING A COINCIDING FACE IN CONTACT WITH SAID COVER WHEREBY TO SEAL THE OPENINGS IN SAID COVER FOR SAID ELECTRODES, SAID ASSEMBLIES BEING ARRANGED IN ROWS LENGTHWISE OF SAID TANK; 